1. Field of the Invention
The present invention relates to a microstrip antenna. Specifically, it relates to a miniaturized microstrip antenna with variable broadband operation.
2. Description of the Related Art
The size of a conventional microstrip antenna is determined by half of the operating wavelength. However, when the conventional microstrip antenna is operates at VHF or UHF band, the size of a conventional microstrip antenna is increased to enhance reception. Consequently, the size of a conventional microstrip antenna can become unduly large when operating at a low resonant frequency.
Examples of existing, conventional microstrip antennea are disclosed as follows: TAIWAN patent no.364228 xe2x80x9cMiniaturized broadband microstrip antennaxe2x80x9d, U.S. Pat. No. 5,453,752 xe2x80x9cCompact broadband microstrip antennaxe2x80x9d and U.S. Pat. No. 5,680,144 xe2x80x9cWideband, stacked doubled C-patch antenna having gap-coupled parasitic elementsxe2x80x9d; or Euro patent no. EP0624578 xe2x80x9cCompact broadband microstrip antennaxe2x80x9d, etc.
In the prior art, a single probe-fed microstrip antenna is proposed and the dual frequency operation is achieved by embedding slots to the microstrip patch. Moreover, since that the frequency ratio of the two operating frequencies is not necessary to be very close, the dual-band design is more simple than the proposed broadband design. By using slots to change the surface current distribution of the resonant modes, dual-frequency operation with a variable ratio of the two frequencies can be obtained. However, to obtain a broadband performance, the two resonant frequencies must be relatively close to one another and the frequency ratio of the two resonant frequencies must meet certain limits.
Furthermore, the current trend of integrated circuit design is for virtually all communication products to become miniaturized in size. Apart from the broadband operation incorporated into the system, the design of the antenna needs to allow for the miniaturization of antenna size according to the overall circuit size.
However, in the conventional art disclosed above, there is currently no such design utilizing slots to both increase the operating bandwidth of the antenna while simultaneously minimizing the antenna size.
The object of the invention is to provide a simple, miniaturized variable bandwidth broadband microstrip antenna with variable broadband operation.
To achieve the objective described above, the present invention provides a microstrip antenna comprised of a ground patch and an isosceles-triangular patch with a pair of primary slots extending from the top angle towards the base angles with a second pair of slots (hereinafter referred to as the second and third slots) connected to and extending downward from each of the primary slots. The primary slots are approximately parallel to the sides of the isosceles-triangular patch while the second and third slots are approximately perpendicular to the base side of the triangle. A substrate connects the ground patch and the isosceles-triangular patch.
The proposed microstrip antenna has a simple structure, low prime cost, is easy to manufacture and achieves size reduction at wide operating bandwidth. The microstrip antenna of the present invention thus has good application value for the manufacturing industry.